Is the human brain a blank slate? or a pre-programmed machine that is ready to take the S.A.T.s right out of the box? Obviously neither, or both as it were. Some have gingerly waded into the nature vs. nuture debate and suggested that the human brain comes pre-wired to receive certain experiences – experience expectant – and thus acknowledge the importance of natural selection in shaping an organism via heritable factors but also the need to be able to use the brain to learn from experience and adapt on the fly.

In their paper entitled, “Nature versus Nurture in Ventral Visual Cortex: A Functional Magnetic Resonance Imaging Study of Twins [DOI:10.1523/JNEUROSCI.4001-07.2007] Thad Polk and colleagues provide a wonderful example of this. The team suggested that the brain (visual system) should be somewhat innately (genomically if you will) prepared to process visual stimuli such as faces and objects, but not so for stimuli such as pseudo words. They proposed to test the role of the genome by comparing patterns of brain activity in identical vs. fraternal twins. If the brain activity patterns were very similar for identical twins, and less so for fraternal twins, then it is likely that the genome plays some role in the generation of brain (at least with respect to blood flow) responses to such stimuli. The team used fMRI to assess 13 pairs of identical twins and 11 pairs of fraternal twins for their brain responses to pictures of faces, houses, chairs and non-word strings on letters as well as control “scrambled” images that were comparable in visuo-spatial frequency.

Interestingly, the team found that for faces and houses, there were significant identical vs. fraternal differences in the “activation maps” of the twins but no such differences for chairs and pseudowords. Thus it seems that the genome plays a role in the way the brain processes faces and houses (or perhaps faces and places in general), but not so much for items that are not found (or weren’t found by our evolutionary ancestors) in a natural setting.

I’m surprised by the chair result … although perhaps being a couch potato is something evolution does not select for.